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sx proto board schematic error? — Parallax Forums

sx proto board schematic error?

CapdiamontCapdiamont Posts: 218
edited 2008-10-13 15:23 in General Discussion
Hello,
The power jack on both sx28 and sx48 is labeled "6-30 VDC" on the schematic PDF. Everywhere else it is 6-9vDC. Though I've heard they can handle 12vDC on the forum. I wish they would be rated for 12vDC. Though I don't think they are capable of doing 30vDC.

Comments

  • JonnyMacJonnyMac Posts: 9,214
    edited 2008-10-13 14:03
    Actually, the LM2940-5 regulator used on that boards will take up to 30v, above that it will shut down.
  • BeanBean Posts: 8,129
    edited 2008-10-13 15:23
    What you have to watch is the regulator will be very hot when the voltage get higher because it must disapate the excess voltage as heat.

    For exaple let's say you are using 500mA (0.5Amps) and using 9V at the input. That would be (9-5)*0.5 in heat or 2 watts.

    If you were using 30 volts at the input it would be (30-5)*0.5 or 12.5 watts in heat (very hot). Surely the regulator would shut down after a short time due to over heating.

    Long story short...It depends on how much current you are using.

    Bean.

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